Photographic shutter with reciprocating sectors and electronic exposure timing device

ABSTRACT

A device for obtaining constancy in the movement of a photographic shutter at even the shortest exposure time having a spring mechanism located between the magnet armature and the member locking the blade driving part. The spring mechanism is releasable by the magnet armature to actuate the member locking the blade driving part. The spring mechanism is so formed that the time interval from the beginning of the actuation of the member locking the blade driving part to its disengagement from the blade driving part is substantially independent of the member locking the blade driving part, and approaches a zero value.

United'States Patent i 72 Inventor Waldemar T.Rentschl er [56]References Cited Black Forest, Germany UNITED STATES PATENTS P 745,2293,376,801 4/1968 Fahlenberg 95/53 221 Filed J ly 1 1968 3 400 645 9/1968K rper 95153.3(X) [45] Patented Mar.9, 1971 e 3 425 328 2/1969 I ChljO95/53(X) [73] Assrgnee Prontor-WerkAl'redGauthier G.m.b.l-l. 3 448 6726/1969 Si 95/530) Calmbach/Bhckhm, Gem! nger [3 2] P i i J l 21, 1967Primary ExaminerJohn M. l-loran [33] m Assistant Examiner-Robert P.Greiner 31] P 41 45 Attorney-March, Gillette and Wyatt ABSTRACT: Adevice for obtaining constancy in the move- [54] P mw ONIC ment of aphotographic shutter at even the shortest exposure 2 8 RETXMgG DEVICE mtime having a spring mechanism located between the magnet Po U armatureand the member locking the blade drivin part. The 6 c s on in 8 hm ispring mechanism is releasable by the magnet armature to ac- [52] US. Cl95/53, tuate'the member locking the blade driving part. The spring95/533, 95/63 mechanism is so formed that the time interval from the[51] Int. Cl..., G03b 9/58, beginning of the actuation of the memberlocking the blade 60% 9/62 driving part to its disengagement from theblade driving part is [50] Field of Search ..95/53,53.3, substantiallyindependent of the member locking the blade 63, 10 (inquired) drivingpart, and approaches a zero value.

2 Sheets-Sheet 1 INVE N TOR Waldemar 7IRenisch/er BY March Gillei te &Wyatt AT TORNEYS Patented March 9, 1971 2 Sheets-Sheet 2 IN VE N TORWaldemar IRentschLer March, Gillette &WyaH

ATTORNEYS PHOTOGRAPHIC SHUTTER WITH RECIPROCATING SECTQBfi ANDELECTRONIC EXPOSURE TIMING DEVICE duration of the timing, the shutterdrive having a device associated therewith to delay the shutter openingmovement to compensate the various time lags of the mechanical lockingcatch of the shutter.

In shutters of the above kind having a driving spring causing theopening and closing movement of the shutter blades, timing is effectedby locking the shutter drive in a position corresponding to the openposition of the blades by means of an electromagneticallyreleasable-stop, and the latter is released again after anelectronically controlled time interval, whereupon the driving springcloses the blades again. The stop is preferably so fashioned that theshutter drive is not held by the magnetic armature itself, but by aseparate catch which in turn is actuated by the released magneticarmature after the magnet coil is deenergized. The magnetic armature issubject to the action of a return spring urging it in the direction ofrelease, the spring being weaker than the holding force of the magnet,so that when the magnet coil is energized the armature is retainedagainst the action of the spring in abutment against the magnet core.With this method of operation the stop cannot be released immediately atthe instant at which the magnet is deenergized, but only after the lapseof some milliseconds. The reason for this is that the magnet armatureand the catch have to move certain distances before the latter v isdisengaged from the locked shutter driving part, which may be the bladedriving ring.

In order to obtain a shutter timing independent of the aforesaid timeinterval existing between the deenergizing of the magnet and the stopbecoming ineffective, and as determined by a photoresistor, it hasalready been proposed to provide a device serving to compensate the saidtime lags of the mechanical stop. This compensating device produces atthe shortest exposure time, e.g., one five-hundredth sec. which is onlydependent on the mechanical shutter drive, a shutter drive actioncompletely unaffected by the stop, since the start contact initiatingthe timing, due to the retarding effect of the compensation mechanism,is closed so early with reference to the fully open position of theshutter, that when the blades are fully open, the magnet armature hasalready left the electromagnet and hence prevents the catch fromengaging the shutter drive.

It has, however, been found that even when using a compensatingmechanism of the kind referred to above, the object aimed at, namely toensure continuous shutter timing over the whole range, could not beattained, more particularly at the fastest shutter speed, i.e., onefive-hundredth sec., where despite the automatic control a certaininstability occurs in this time range; it was found that not anintermediate speed, for instance a time value between one five-hundredthand one two hundred and fiftieth sec. but alternatively either onefivehundredth sec. or one two hundred and fiftieth see. was obtained.Investigation of this phenomenon showed the occurrence of certaindeviations in the movement time of the stop mechanism consistingessentially of the magnet armature and catch, depending upon whetherbefore releasing the drive stop the catch is biased or unbiased by theshutter drive. it has been found that if the catch is biased by theshutter drive the return movement of the stop member, from the instantof deenergization of the armature, occupies more time than in the casein which the parts can move without prior biasing by the driving force.This is because if the stop is in the biased state it has to be releasedagainst the frictional force or the prevailing surface pressure existingbetween shutter drive and the catch.

The present invention resides in means for obtaining constancy in themovement of the device serving the exposure timing even at the shortestexposure time, without any significant additional structural-complexityin the shutter systems of the kind referred to.

The invention consists in that between the magnet armature and the catchlocking the blade driving part a spring relay is located which isreleasable by the magnet armature to actuate the catch and is so formedthat the time interval from the beginning of the actuation of the catchto its disengagement from the blade driving part is substantiallyindependent of the catch loading, and approaches a zero value. In thisway the period necessary for disengagement of the catch biased orunbiased, by the shutter drive is substantially constant, so that fromthe shortest to the longest exposure time of the shutter the timingtakes a continuous course.

In a simple embodiment of a spring relay readily adaptable to thestructural conditions of a shutter with electronic timing, there is arotatably mounted two-armed actuating lever subject to the action of arelatively powerful spring, one lever arm of which is adapted to belocked by means of a pawl movable by the armature lever from the catchposition, and the other lever arm of which cooperates with the catch.This arrangement may be simplified by mounting the two-armed actuatinglever on the same pivot as the armature lever.

To ensureas simple as possible an operation of a shutter equipped with aspring relay and having an electronic timing device, according to afeature of the invention a cocking arm is moved during the cockingprocess of the'shutter, by means of which arm the actuating lever isbrought into the cocking position and the magnet armature caused to abutagainst its magnet. To ensure an action unaffected by manufacturinginaccuracies, the cocking arm is formed by two levers mounted on thesame pivot and positively supported against one another, one lever ofwhich cooperates with a movable part of the shutter drive mechanism andthe other with the actuating lever of the spring relay and the armaturelever.

Reference should now be made to the accompanying drawings, in which:

FIG. I is an electronic shutter with its compensation mechanismin thecocked position;

FIG. 2 is a fragmentary view of the shutter shown in FIG. I with theshutter blades in the open position and the locking mechanism still inthe stop position;

FIG. 3 is a further fragmentary view of the shutter blade drivemechanism, in which the locking mechanism has just released the returnmovement to transfer the blades into the closing position;

FIG. 4 is a diagram of the time interval divisions which occur betweenthe deenergizing of themagnet of the timing device and the disengagementof the catch of the locking mechanism; and

FIG. 5 is a fragmentary section through the electronic shutter on theline V-V of FIG. 2.

The numeral 1 in the drawings denotes the base plate of a photographicshutter which is arranged in a shutter housing 2 and provided with alens socket la. The base plate 1 serves to mount the shutter drivemechanism, which comprises a cocking and driving shaft 4, a driving disc5 fixed thereto, a driving spring 6 acting thereon and a drive pawl 7connected to the driving disc, the free end of the pawl cooperating sowith the driving ring 8 of the shutter blades 9 through a lug 8a so thatwhen the driving disc 5 rotates in the direction of the arrow, thedriving ring 8 and the blades 9 execute a reciprocating movement. Tolock the driving disc 5 in the cocked position shown in FIG. 1 atwo-armed stop lever 10 is used, one lever arm of which is engaged bythat of a further two-armed release lever 11 only part of which is shownin FIG. 1, the other part being indicated by a chain-dotted line. Thislever is actuated by means of the camera release 12, also only partshown in FIG. 1, which is in operational engagement with the lever illvia suitable intermediate members which in the drawings are shown onlyby a chain-dotted line.

To hold the blades SI of the shutter open for a duration determined byan electronic switching device to be described in detail hereinafier,the driving ring 8 has a further lug 8b projecting through a slot in thebase plate 1, which lug is locked by a spring-loaded catch 14, when theshutter blades are in an open position as shown in FIGS. 2 and 5. Thiscatch as shown in FIG. is provided for this purpose with an engaging pin14a and a laterally projecting lug 14b, which by means of a spring 15acting on the catch is adapted to be moved into the movement range ofthe lug 8b provided on the driving ring 8 and to be moved out of thestop position by means of an actuating lever 17 rotatably mounted on thebase plate 1, this lever 17 being acted upon by a relatively powerfulspring 16. The actuating lever 17 is mounted on a pin 13 and has twoarms 17a and 17b and is adapted to be locked in a cooked position by apawl 18. Mounted coaxially with the actuating lever 17 formed as aspring relay on the pin 13 there is a one-armed lever 19, at the freeend of which an armature 20 is hinged. An electromagnet 21 connected incircuit with an electronic timing device acts on the armature 29. Thetiming device has a delay circuit 23 of known type and not shown infurther detail in the drawings. This circuit is preferably formed as atrigger circuit comprising several transistors with a feedback path.

' The time determining members comprising the photoresistor R andcapacitor C are located in thecircuit with a bat tery B adjacent to theelectromagnet 21 and the electronic delay circuit 23. Apart from this RCnetwork there is a main switch S actuable by the release mechanism 11 ofthe shutter, a start contact S, initiating charging of the capacitor C,and a switch 8, which changes over the photoresistor R at the beginningof the starting movement of the driving ring 8 from a moving coil meter1 to the circuit of the timing device. The load start switch S, normallyshort circuits the capacitor C shown in FIG. 1, whilst the moving bladeof the switch S establishes an electric connection between photoresistorR and the moving coil meter J. The starting movement of the driving ring8, causes the pins 8c and 8d to transfer the two moving blades away fromthese previously made contacts; the switch S, changes over thephotoresistor R to the circuit of the electronic timing device, and theswitch S removes the short circuit on the capacitor C and henceinitiates shutter timing. The pawl 18 is provided to lock the springrelay 16, 17 and biased by a spring 25, is so formed that it constantlyparticipatesin the movement of the armature lever 19, the latter beingprovided with an engaging pin 27 acting as support of the pawl. A devicefor compensating the time constant of the aforesaid mechanical catch andwhich is formed by a brake lever 29 subject to the action of a spring 28and a rotatably mounted heavy disc 30 operationally connected therewith,cooperates with the driving ring 8.

Referring to the aforesaid spring relay consisting of spring 16 andactuating lever 17 in connection with the aforesaid compensationmechanism 28 to 30, the object of these devices is to obtain a range ofcontinuous shutter speeds, all of which, even to the fastest speeds,remain constant, independently of whether the driving ring 8 has beenlocked in the shutter open position or not. Thus, catch 14 is no longerreleased as hitherto directly by the magnet armature, but by the springrelay 16, 17 located between the latter and the catch 14 acting on thedriving ring 8. This spring relay on release actuates the catch 14 withconsiderable force to reducethemovement time for this catch, up to theinstant of disengagement at the lug 8b of the driving ring 8, to as nearzero as possible. The time required for the movement of the catch 14from a stop position is substantially the same, whether it is loaded ornot. The driving force of the spring relay 16, 17 is made as great aspossible for this purpose. Apart from a certain maximum cockingpressure, the driving force of the spring relay 16, 17 is indirectlylimited by the holding force of the electromagnet 21. The latter hasalways to be greater than the return force of the return spring 31acting on the armature lever 19. On the other hand, the return force ofthis spring must be great enough to cancel the latching of the springrelay 16, 17 by the pawl 18 without appreciable loss of time.

On the presumption that the movement time of the catch M both in theloaded and unloaded state is substantially uniform, as shown by FIG. 4,the whole time interval T occurring between the deenergizing of theelectromagnet 21 and the disengagement of the catch from the drivingring 8 can be compensated by the compensating mechanism 28 to 30. Thistime interval T is divided into the following time sections:

t movement time of the magnet armature 20 from leaving the electromagnet21 to the release of the spring relay 16, 17 by the pawl 18;

t starting time of the spring relay 16, 17 to contact with the catch 14;and

t movement time of the catch 14 to the disengagement of the lug 8b ofthe driving ring 8.

From this diagram it is evident that the time sections t, and t, arecompletely independent of whether the catch 14 is loaded or not. Theymay thus be completely compensated for all shutter timings by means ofthe compensating mechanism 28 to 80. The only difference between thetiming of the loaded and unloaded catch 14 exists only with regard tothe time section i The spring relay 16, 17 which by means of arelatively powerful spring causes this time section to approximate tozero, thus greatly reduces timing variations regardless of whether thecatch 14 is to be moved loaded or unloaded from the stop position. Hencethe time section t may also be taken into consideration by means of thecompensating mechanism 28, 30, whereby an effective compensation of theentire time interval T consisting of the aforesaid three time sections1, to may be obtained.

In order to enable both the spring relay 16, 17 and the armature lever19 to be moved dependent upon the cocking operation into their positionsassumed before the shutter action, against the action of the springs 16or 31 engaging these parts, a cocking arm rotatably mounted on an axis34 is provided, formed by two coaxially mounted levers 35 and 36. Theselevers in turn are positively held against one another by an excesstension spring 37 and a laterally bent over lug 35a. To move the cockingarm 35 to 37, the driving disc 5 has a laterally extending actuating pin5a which is so arranged that during the cocking operation of theshutter, pressure is exerted on the free end of the cocking arm, whichpressure is transmitted via a pin 35b provided on the lever both to theactuating lever 17 and the armature lever 19.

The method of operation of the shutter system described above is asfollows:

Depressing the camera release 12 causes the release lever 11 and thecatch lever 10 to move therewith, the result of which is that the mainswitch S is closed and the shutter drive is released for action. Onclosure of switch S, the electromagnet 21 is connected to the batteryvoltage, and the blades 9 are opened after the delay of the openingmovement of the drive ring 8 caused by the compensating mechanism 28 to30, the switches S and S being simultaneously actuated. On reaching theshutter open position the catch 14 as shown in FIG. 2 drops intoposition in front of the lug 8b of the driving ring 8 and hence locksthe whole driving system. This condition persists until the timingdevice cancels the magnetic field of the electromagnet 21 andconsequently releases armature 20. The armature lever 19 under theinfluence of the spring 31 is set in motion and thus by engaging the pin27, disengages the pawl 18 from the spring relay 16, 17. The actuatinglever 17 thus released, rotates in a clockwise direction on its bearingpin 13 under the influence of the relatively powerful spring 16,striking with the arm 17b against the pin 14a arranged on the catch 14with the result that the catch is rapidly moved out of the lockingposition. Consequently, as shown in HO. 3, the driving system is againable to move and to transfer the blades 9 into the closed position.

The spring relay 16, 17 described above and located between the magnetarmature 20 and catch M, in combination with the compensating mechanism28 to 30, is not limited to specific use in electronic shutters having ashutter blade system comprising several blades. This combination may bepart of which executes a reciprocating movement for opening and closingthe lens aperture. ,Thus, the spring relay l6, 17

spring relay consists of a rotatably mounted two-armed actuat- 7 couldalso be installed in an electronic shutter the blade system of which hadonly a single segment. The essential feamechanical locking means of theshutter, electronic timing means controlling an electromagnetic armaturebiased by a return spring, a mechanical locking means including a catchactuated by the armature, said catch acting to lock said driving partfor the duration of the. timing, spring relay means acting on saidcatch, said spring relay means being between said electromagneticarmature and said catch locking the driving part, said spring relaymeans being releasable by said armature and actuating said catch so thatthe time interval from the vbeginning of the actuation of said catch toits disengagement from said driving part approaches a zero value.

2. Ashutter according to claim l wherein the spring means ture is thatthe blade driving part executes an oscillating movecomprise a springrelay.

3. A photographic shutter according to claim 1, wherein the ing leverwhich is subject to the action of a spring, one lever arm of which canbe locked by means of a pawl which can be moved out of the stop positionby the armature lever, the

other lever arm cooperating with the catch.

lever carrying the electromagnet armature.

5. A photographic shutter according to claim 3 having a cocking armwhich is moved during the cocking of the shutter, the movement of thecocking arm bringing the actuating lever into the cocking position andthe electromagnet armature into contact with its electromagnet.

6. A photographic shutter according to claim.5 wherein the cocking armis formed by two levers mounted on the same pivot and positively heldagainst one another by means of an excess tension spring, one lever ofwhich cooperates with a movable part of the shutter driving mechanismand the other with the actuating lever of the'spring' relay and theannature lever.

1. A photographic shutter having a reciprocating driving part acting onthe shutter blades, said driving part having a retarding meansassociated therewith delaying the opening movement and serving tocompensate time lags of the mechanical locking means of the shutter,electronic timing means controlling an electromagnetic armature biasedby a return spring, a mechanical locking means including a catchactuated by the armature, said catch acting to lock said driving partfor the duration of the timing, spring relay means acting on said catch,said spring relay means being between said electromagnetic armature andsaid catch locking the driving part, said spring relay means beingreleasable by said armature and actuating said catch so that the timeinterval from the beginning of the actuation of said catch to itsdisengagement from said driving part approaches a zero value.
 2. Ashutter according to claim 1 wherein the spring means comprise a springrelay.
 3. A photographic shutter according to claim 1, wherein thespring relay consists of a rotatably mounted two-armed actuating leverwhich is subject to the action of a spring, one lever arm of which canbe locked by means of a paWl which can be moved out of the stop positionby the armature lever, the other lever arm cooperating with the catch.4. A photographic shutter according to claim 3, wherein the two-armedactuating lever is mounted on the same pivot as a lever carrying theelectromagnet armature.
 5. A photographic shutter according to claim 3having a cocking arm which is moved during the cocking of the shutter,the movement of the cocking arm bringing the actuating lever into thecocking position and the electromagnet armature into contact with itselectromagnet.
 6. A photographic shutter according to claim 5 whereinthe cocking arm is formed by two levers mounted on the same pivot andpositively held against one another by means of an excess tensionspring, one lever of which cooperates with a movable part of the shutterdriving mechanism and the other with the actuating lever of the springrelay and the armature lever.